This invention relates to a small autoclave and to a process for bonding composite lenses.
Ophthalmic and sunglass lenses have been used for many years. The optical industry has faced difficult problems in the manufacturing, handling and packaging of the optical glass materials. Such glasses are sensitive to mechanical stress, scratch easily and require the utmost care in handling to insure that a safe precision product is provided to the user. More recently the problems associated with manufacturing, handling and packaging of ophthalmic lenses became more difficult because of the use of composite materials for ophthalmic applications, namely, glass-plastic laminates. Generally, such composites are made of at least two materials: an inorganic glass lens prefinished by grinding and polishing to prescription on both of its major surfaces, and a composite organic material in the form of a thin film bonded to the glass lens and forming therewith the "uncut" form of the ophthalmic lens. If desired, the uncut lens is then tinted to various colors to provide luminous transmission characteristics thereto. For mounting, the completed lens is edge finished and installed in frames by conventional methods. The process for making such composite lenses generally includes the cleaning, drying and inspection of the inorganic glass surface, the positioning of the organic film material onto the glass lens, the lamination or bonding of the two components, dying or tinting the composite, and "fixing" the dye thereto.
In the above-described process the necessity of safe and convenient handling of the optical material should be apparent to those skilled in the optical art. Specifically, the highly polished active surfaces of the lens must remain free from contact with any hard surface whatsoever during the manufacturing, handling and storage thereof. It has been observed that when the active surfaces of an ophthalmic lens contact any hard substance they tend to become marred making subsequent processing steps futile, or in the finished product resulting in impaired efficacy of transmission of light therethrough.
One facet of composite lens manufacturing involves chemical and physical bonding of the plastic wafer to the prefinished glass lens accomplished under suitable conditions of heat and pressure. The combined effect of pressure and temperature must be adequate to eliminate gaseous inclusions and to develop sufficient adhesive forces between the plastic wafer and the glass. However, this effect cannot be excessive so as not to cause alterations in properties of the layers being laminated. For this reason, it is necessary to control the conditions of the lamination process.
It has been observed that large industrial sterilizers or autoclaves are not well suited for bonding composite lenses for reasons of economy and design. They are: not designed for small batch processing characteristic of lens manufacturing; expensive to operate with small batches; illsuited to homogeniously maintain proper temperature/pressure conditions therein; and not equipped with proper lens holders or carriers for preventing contact between optical surfaces of the lenses being autoclaved and the environment.
Accordingly, it is an object of the present invention to provide an autoclave equipped with a lens tray or holder.
It is another object of the invention to provide an autoclave in which pressure and temperature requirements are easily maintained.
It is a further object of the present invention to provide an autoclave adapted to small batch operations.
It is still another object of the present invention to provide a process for bonding composite lenses utilizing a small, safe and inexpensive autoclave.